Emerging evidence is revealing that alterations in gut microbiota are associated with colorectal cancer (CRC). However, very little is currently known about whether and how gut microbiota alterations are causally associated with CRC development. Here we show that 12 faecal bacterial taxa are enriched in CRC patients in two independent cohort studies. Among them, 2 Porphyromonas species are capable of inducing cellular senescence, an oncogenic stress response, through the secretion of the bacterial metabolite, butyrate. Notably, the invasion of these bacteria is observed in the CRC tissues, coinciding with the elevation of butyrate levels and signs of senescence-associated inflammatory phenotypes. Moreover, although the administration of these bacteria into Apc^Δ14/+ mice accelerate the onset of colorectal tumours, this is not the case when bacterial butyrate-synthesis genes are disrupted. These results suggest a causal relationship between Porphyromonas species overgrowth and colorectal tumourigenesis which may be due to butyrate-induced senescence.

Background: The “watch-and-wait” approach is a common treatment option amongst patients with locally advanced rectal cancer (LARC). However, the diagnostic sensitivity of clinical modalities, such as colonoscopy and magnetic resonance imaging to determine pathological response, is not high. We analysed the clinical utility of circulating tumour DNA (ctDNA) of patients with LARC to predict response to preoperative therapy and postoperative recurrence. Methods: A serial ctDNA analysis of 222 plasma samples from 85 patients with LARC was performed using amplicon-based deep sequencing on a cell-free DNA panel covering 14 genes with over 240 hotspots. Results: ctDNA was detected in 57.6% and 22.3% of samples at baseline and after preoperative treatment, respectively, which was significantly different (P = 0.0003). Change in ctDNA was an independent predictor of complete response to preoperative therapy (P = 0.0276). In addition, postoperative ctDNA and carcinoembryonic antigen (CEA) were independent prognostic markers for risk of recurrence after surgery (ctDNA, P = 0.0127 and CEA, P = 0.0105), with a combined analysis having cumulative effects on recurrence-free survival (P = 1.0 × 10^–16). Conclusions: Serial ctDNA analysis may offer clinically useful predictive and prognostic markers for response to preoperative therapy and postoperative recurrence in patients with LARC.

Background Accumulating evidence suggests that radiotherapy success has an immune‐associated component. The immunogenomic profiles associated with responses to chemoradiotherapy (CRT) were assessed in patients with locally advanced rectal cancer in this study. Methods CD8+ tumour‐infiltrating lymphocyte (TIL) and stromal lymphocyte densities were assessed by immunohistochemistry using pretreatment biopsies from patients with advanced rectal cancer who had preoperative CRT. Whole‐exome sequencing and gene expression microarray analysis were conducted to investigate the genomic properties associated with the response to CRT and CD8+ TIL density. Response to CRT was determined based on Dworak tumour regression grade (TRG); tumours with complete (TRG 4) or near‐complete (TRG 3) regression were grouped as good responders, and those with TRG 1 as non‐responders. Results Immunohistochemical examinations (275 patients) showed that pre‐CRT CD8+ TIL density was associated with better response to CRT and improved recurrence‐free survival, whereas pre‐CRT stromal CD8+ cell density was not associated with either response to CRT or recurrence‐free survival. Whole‐exome sequencing (74 patients) showed that the numbers of single‐nucleotide variations (SNVs) and neoantigens predicted from SNVs were higher in good responders than in non‐responders, and these correlated positively with CD8+ TIL density (r _S = 0·315 and r _S = 0·334 respectively). Gene expression microarray (90 patients) showed that CD8A expression correlated positively with the expression of programmed cell death 1 (PDCD1 ) (r _S = 0·264) and lymphocyte‐activation gene 3 (LAG3 ) (r _S = 0·507). Conclusion Pre‐CRT neoantigen‐specific CD8+ T cell priming may be a key event in CRT responses where immune checkpoint molecules could be useful targets to enhance tumour regression.

Inhibition of the programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) axis in combination with radiotherapy may be a promising approach to treat cancer. In the present study, we aimed to evaluate serum soluble PD-1/PD-L1 levels in patients with advanced rectal cancer treated with neoadjuvant chemoradiotherapy (CRT). Serum soluble PD-L1 and PD-1 levels were measured using an enzyme-linked immunosorbent assay before and after CRT in 117 patients with low rectal cancer. Changes in the levels of sPD-L1/PD-1 after CRT, and the correlation between sPD-L1/PD-1 level and clinicopathological characteristics or disease-free survival (DFS) were evaluated. sPD-L1 levels significantly increased after CRT (p < 0.0001), whereas sPD-1 levels did not change significantly (p = 0.1050). High sPD-L1 before CRT was significantly associated with younger age (p = 0.044), and after CRT, with lymphovascular invasion (p = 0.021). High sPD-1 before and after CRT was significantly associated with a longer distance of the tumor from the anal verge (both p < 0.001). There was no correlation between sPD-L1 level and local PD-L1 expression on stromal immune cells. High sPD-L1 level after CRT tended to be associated with worse DFS (p = 0.0752). The multivariate analysis could not demonstrate an independent association for sPD-L1 levels after CRT with DFS. Significant increase of sPD-L1 levels after CRT suggests that anti-PD-L1 therapy might be a potential treatment strategy in combination with CRT in advanced rectal cancer.

BACKGROUND AND AIM: Various factors make complete en bloc resection by endoscopic techniques alone of some laterally spreading colorectal tumors difficult or unsafe. Drawing on recent radical developments in endoscopic and laparoscopic techniques for managing colorectal lesions, we aimed to develop a safe resection procedure by using a combination of laparoscopy and endoscopy. We have named this procedure laparoscopic endoscopic cooperative colorectal surgery. PATIENTS: We have performed this procedure on 3patients who had laterally spreading colorectal tumors. The factors contraindicating endoscopic submucosal dissection were submucosal fibrosis because of previous endoscopic mucosal resection in 1 patient and multiple surrounding diverticula in 2 patients. TECHNIQUE: The patient is placed under general anesthesia and 5 ports are inserted. Following confirmation of the tumor location by endoscopy and laparoscopy, the colon wall at this site is exposed. First, a mucosa-to-submucosa dissection circumferential to the lesion with an appropriate safety margin is performed endoscopically. Complete full-thickness dissection and excision is then performed by using ultrasonic activating scissors, endoscopy, and laparoscopy cooperatively. The excised lesion is withdrawn intraluminally with endoscopic forceps. The opened colon is then closed with laparoscopic linear staplers. RESULTS: The mean operating time and blood loss in this series were 205 minutes and 13 mL. There were no intraoperative or postoperative complications. Histological examination revealed tubular adenomas with severe dysplasia and adequate surgical margins in all cases. CONCLUSION: Laparoscopic endoscopic cooperative colorectal surgery involves removal of a minimal length of colon and is a feasible procedure for en bloc resection of some colonic lateral spreading tumors that would be difficult to resect endoscopically.

Background There is a lack of large studies focusing on the prognostic significance of lateral lymph node (LLN) metastasis following LLN dissection (LLND) in rectal cancer. The aim of this study was to evaluate the prognostic impact of LLN metastases on survival of patients with advanced low rectal cancer. Methods Consecutive patients with locally advanced, but not metastatic, extraperitoneal rectal cancer treated with neoadjuvant (chemo)radiotherapy plus total mesorectal excision between 2004 and 2015 were included in the study. LLND was performed when pretreatment imaging documented enlarged LLNs (7 mm or greater in size). Localization of nodal metastases and long‐term outcomes were analysed. Kaplan–Meier analysis was used to compare the survival of patients with ypN0 disease with that of patients with mesorectal ypN+/LLN− status and patients with positive LLNs. The Cox proportional hazards model was used to evaluate predictors of disease‐free survival (DFS) and local recurrence. Results A total of 613 patients were included in the study; LLND was performed in 212 patients (34·6 per cent) and 57 (9·3 per cent) had LLN metastasis. Patients with LLN metastasis had improved DFS and local recurrence cumulative incidence rates compared with patients with mesorectal ypN2+/LLN− disease (DFS: P = 0·014; local recurrence: P = 0·006). Although the DFS rate of patients with LLN metastasis was worse than that of patients with ypN0 disease (P < 0·001), the cumulative incidence of local recurrence was similar (P = 0·491). In multivariable analysis, residual LLN metastasis was not an independent predictor of worse DFS or local recurrence. Conclusion LLN metastasis is not an independent predictor of local recurrence or survival. Survival of patients presenting with LLN metastasis after (chemo)radiotherapy was intermediate between that of patients with ypN0 status and those with mesorectal ypN2 positivity.